The invention relates to a method for producing III-V materials by metal-organic chemical vapor deposition (MOCVD) and, more particularly, to a method for producing aluminum-indium-antimony materials by MOCVD.
Metal-organic chemical vapor deposition (MOCVD), alternatively called organometallic vapor-phase epitaxy (OMVPE) or other combinations of these terms such as metal-organic vapor phase epitaxy (MOVPE), is an epitaxial crystal growth technique yielding high-quality low-dimensional structures for semiconductor devices, both optoelectronic and electronic. The growth of semiconductor III-V compounds by MOCVD involves introducing metered amounts of the group III alkyls and the group V hydrides as gases into a reactor that contains a heated susceptor. The growth takes place at the susceptor on a substrate. The reactor system may have various configurations including a reactor chamber operated under a vacuum with a rotating susceptor (Breiland W. G. and Evans, G. H., J. Electrochem. Soc., 1991, 138(6), 1806-1816; incorporated by reference herein) or a quartz reactor chamber operated at atmospheric pressure with a stationary susceptor (Biefeld R. M., Hills, C. R., and Lee, S. R., J. of Crystal Growth, 1988, 91, 515-526; incorporated by reference herein).
AllnSb materials are of interest for their potential applications in a variety of optoelectronic and electronic devices such as infrared detectors, resonant tunneling diodes, magnetic field sensors, and laser diodes as well as a variety of other semiconductor heterostructures. In particular, these materials can be used as confinement materials in 2-6 .mu.m, mid-infrared optoelectronic and heterojunction devices. Emitters in this wavelength range have potential uses as chemical monitors and in infrared countermeasures.
Devices using AllnSb have been successfully prepared by molecular beam epitaxy (MBE). For example, Whitehouse et al. (Whitehouse, C. R., McConville, C. F., Williams, G. M., Cullis, A. G., Barnett, S. J., Saker, M. K., Skolnick, M. S., and Pitt, A. D., Mat. Res. Soc. Symp. Proc., 1990, 198, 283-288) describe the growth of high-quality InSb/lnAISb structures by MBE on InSb substrates. Saker et al. (Saker, M. K., Whittaker, D. M., Skolnick, M. S., McConville, C. F., Whitehouse, C. R., Barnett, S. J., Pitt, A. D., Cullis, A. G., and Williams, G. M., AppI. Phys. Lett., 1994, 65(9), 1118-1120) discuss quantum confinement in InSb-Al.sub.x In.sub.1-x, Sb (0.08&lt;.times.&lt;0.30) structures grown on InSb (100) substrates using MBE. MOCVD is preferred in some applications over MBE, generally a more expensive technique, when large-scale production is desired and for optoelectronic devices such as light-emitting diodes and lasers. MOCVD has potential advantages that include the capability to rapidly vary the composition over wide ranges, good layer growth control, and simpler handling due to the standard- or low-pressure conditions. The technique is attractive in its ability to grow uniform layers, its low background doping density and sharp interfaces, and its relative simplicity compared to other growth methods for commercial applications.
Several investigators have grown AlSb by MOCVD, although little mention has been made regarding purity. Leroux et al. (Leroux, M., Tronson-Carli, A., Gibart, P., and Verie, C., J. of Crystal Growth, 1980, 48, 367-378) prepared AlSb on SiO.sub.2 substrates using MOCVD, noting that growth methods like hydride VPE or liquid phase epitaxy are difficult to implement for aluminum compounds because gaseous aluminum chloride etches the quartz tubes and molten aluminum etches common crucibles. MOCVD was found to be a reliable method to grow thin films of AlSb, avoiding problems of aluminum reactivity and inhomogeneity that occur on growth from the melt.
Biefeld et al. (Biefeld, R. M., Allerman, A. A., and Pelczynski, M. W., Appl. Phys. Lett., 1996, 68(7), 932-934) have also grown high-quality AlSb by MOCVD with low carbon concentration. Biefeld et al. also demonstrated the growth of low carbon AlAs.sub.0.16 Sb.sub.0.84 by MOCVD. Biefeld et al. also note that growing aluminum compounds by MOCVD often fail because the use of conventional precursors, such as trimethylaluminum and trimethylantimony (TMSb) or triethylantimony (TESb) has resulted in material with carbon and oxygen concentrations exceeding 1.times.10.sup.19 cm.sup.-3, with rough surface morphologies. Known to those skilled in the art is that Al-containing materials prepared using MOCVD tend to have larger concentrations of both O and C impurities when compared to the Ga-containing analogue. The presence of these impurities in Al-containing semiconductors is due to the strength of the bond between Al and O or C when compared to the bond strength of Al to P, As, or Sb. Biefeld et al. report significant reductions of C and O incorporation by using trimethylaminealane and triethylantimony.
Jones (Jones, A. C., J. of Crystal Growth, 1993, 129, 745) attempted the growth of compounds incorporating both In and Al, in the form of trimethylaminealane (TMAAI), but severe premature reactions occurred, preventing or hindering growth of the desired crystalline material. Jones attempted the growth of AllnAs materials with TMAAI and found that premature reactions occurred, even at reduced pressures, when a high concentration of Al, in the form of TMAAI, was present in combination with (CH.sub.3)In and AsH.sub.3, which precluded successful AllnAs growth.
Useful would be a method to prepare AllnSb by MOCVD to obtain a high-quality material that can be incorporated in optoelectronic and electronic devices. Because of the difficulties mentioned herein in preparing AllnSb materials by MOCVD, the prior art provides no solutions to this unmet need.